The radiocommunication systems generally comprise an amplifier module connected between, on the one hand, a radiofrequency module and, on the other hand, an antenna system. The function of such a module is to amplify the wanted signal as well in transmission as in reception. More particularly, the amplified wanted signal transmitted via the antenna system must be powerful enough to reach the required range, occupied by a frequency band corresponding to the waveform employed to achieve the performance levels, particularly in terms of desired bit rate, while observing the necessary normative and regulatory constraints.
An amplifier module can mainly be broken down in signal power amplification devices and wanted signal filtering devices. The filtering devices must be adapted to wanted signals whose waveform occupies a particularly wide bandwidth. As an example, the radiocommunication software systems that employ frequency-evasion waveforms can send and/or receive in a frequency range from 30 MHz to 3 GHz (or the frequency band commonly designated by the acronym VHF, standing for Very High Frequency, and the frequency band commonly designated by the acronym UHF, standing for Ultra High Frequency). The filtering devices must consequently guarantee compatible operation of the frequency-evasion waveforms, namely compatibility of the tuning speed and mastery of the transmitted spectrum. The filters called agile filters can be used in particular to address this issue. Among the agile filters, there are capacitance-weight filters, also called tractable filters.
FIG. 1 is a circuit diagram of a capacitance-weight filter according to the state of the art. The filter comprises a main board 1. The main board 1 comprises an input E via which a signal to be filtered is received, and an output S to which a filtered signal is delivered. The main board 1 comprises two magnetically-coupled oscillating circuits. The main board 1 also comprises capacitance weights (in FIG. 1, eight capacitance weights for each oscillating circuit designated by the letters A to H). The number of capacitance weights is linked to the extent of the frequency band covered by the filter and the intrinsic frequency band of said filter. Each capacitance weight A . . . H in FIG. 1 comprises a capacitor and a diode. Each capacitance weight is controlled by signals received from a management and control board 2. The management and control board 2 converts the commands that it receives on inputs CA . . . CH into commands for the capacitance weights A . . . H. The management and control board 2 and the main board 1 are normally implemented on two separate and interconnected electronic boards.
The capacitance-weight filters according to the state of the art can be used to filter powerful signals (for example, of the order of 50 W), by being agile, selective and limiting the losses. However, the bulk of such filters is a problem. It is possible to limit the bulk of such a filter by using three-dimensional mounting technique. However, this workaround then introduces a significant additional cost. In practice, the design of such a filter is made more complex, the fabrication methods more costly (fabrication and mounting then being at least partly carried out manually), and debugging, if not difficult, at least difficult to reproduce from one filter to another. More generally, the problem raised is that of the miniaturization of this type of filter in an automated industrial environment without degrading the technical performance levels of such a filter. Therefore, there is a need to solve the problems described above.